A linear low-density metallocene polyethylene resin, a linear low-density metallocene polyethylene packaging film suitable for polysilicon packaging bags, and a preparation method thereof

Abstract

The present invention relates to a linear low-density metallocene polyethylene resin, a linear low-density metallocene polyethylene packaging film suitable for polysilicon packaging bags and a preparation method thereof, belonging to the technical field of petrochemical industry. The latter comprises the following steps: using a material comprising ethylene, hydrogen, comonomer, nitrogen and a condensing agent as a raw material, adjusting the gas-phase components in the reactor, and carrying out a polymerization reaction by using a metallocene catalyst to obtain a linear low-density metallocene polyethylene powder; mixing the linear low-density metallocene polyethylene powder, an antioxidant and a co-antioxidant, and then carrying out kneading and melting to obtain a linear low-density metallocene polyethylene resin. The linear low-density metallocene polyethylene packaging film suitable for polysilicon packaging bags comprises: an inner layer, comprising mLLDPE and a slip agent. By using the method of the present invention, a linear low-density metallocene polyethylene packaging film with high purity and puncture resistance and suitable for polysilicon packaging bags can be obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of petrochemical engineering, and particularly relates to a linear low-density metallocene polyethylene resin, a linear low-density metallocene polyethylene packaging film suitable for polysilicon packaging bags, and a preparation method thereof. Background Art

[0002] At present, polysilicon is widely used in the semiconductor and solar energy industries. Since it is extremely afraid of pollution, it needs to be packaged before transportation. Currently, polyethylene packaging bags are generally used to package polysilicon. For example, a Chinese patent document with the publication number CN105017601A discloses a polysilicon packaging film, which is prepared from raw materials including three different melt indexes of LDPE and lubricants; the preparation raw materials may also include a polyimide oligomer mixture and 1,3,5-triaminobenzene. However, due to the low puncture resistance of the packaging bag, the polysilicon blocks are vibrated and jolted during transportation and storage, and the packaging bag is cut and punctured by the sharp-edged polysilicon blocks, exposing the polysilicon blocks to the air, resulting in the pollution of the polysilicon blocks.

[0003] At present, in order to improve the puncture resistance of polysilicon packaging bags, the prior art generally improves the performance of polysilicon packaging bags by changing the form of the packaging bag, adding processing aids and formulas, etc.

[0004] A Chinese patent document with the authorization publication number CN219707743U discloses a clean PE bag for polysilicon packaging, including a first bag body and a second bag body. The first bag body is placed inside the second bag body, and a bubble film is arranged inside the first bag body with the bubble surface facing inward. By laying a bubble film inside the first bag body and making the bubble film face inward, the contact surface between the polysilicon and the first bag body is reduced, and the risk of the polysilicon piercing the first bag body is reduced; by installing magic tapes at the upper end and middle part on one side of the second bag body, the first bag body is tightened by the second bag body, avoiding the movement of the first bag body inside the second bag body, reducing the friction between the polysilicon, and further reducing the risk of the polysilicon piercing the first bag body.

[0005] A Chinese patent document with the authorization publication number CN220683315U discloses a high-purity polysilicon packaging bag, including an inner bag and an outer bag. Both the inner bag and the outer bag have a first side, a second side, a first edge, a second edge, and a third edge. By sealing the edges, a chamber is formed between the two sides. The inner bag is placed inside the outer bag with a gap. The chamber of the inner bag is the first space, and the space between the inner bag and the outer bag is the second space; the inner bag also has mesh holes, and the distribution density of the mesh holes is between 10% and 90%; high-purity polysilicon is placed in the first space, and the silicon powder falling off is collected in the second space; a high-purity polysilicon packaging bag formed by sealing the edges of the two sides, and mesh holes are opened on the inner bag, facilitating the falling of the silicon powder generated by the friction between the high-purity polysilicon.

[0006] A Chinese patent document with the publication number CN113232393A discloses an electronic-grade polysilicon packaging bag and its production method. The electronic-grade polysilicon packaging bag includes an inner layer, a middle layer, and an outer layer. The inner layer includes 100% by weight of LLDPE. The middle layer includes 68-72% by weight of metallocene PE and 32-28% by weight of LLDPE. The outer layer includes 85% by weight of LLDPE and 15% by weight of auxiliary materials, and the auxiliary materials contain conductive materials. The thickness ratio between the inner layer, the middle layer, and the outer layer is 2:4:4. The electronic-grade polysilicon packaging bag with this structure makes full use of the tensile resistance, penetration resistance, impact resistance, and tear resistance of LLDPE, as well as the penetration resistance of metallocene PE. By adopting the structure of pure LLDPE in the inner layer, the surface metal precipitation rate can be effectively reduced, and it is very suitable for the packaging of polysilicon.

[0007] However, the polyethylene used in the prior art may itself contain a certain amount of impurities. For polysilicon used in the electronics industry, if the impurity concentration on the surface of the packaging bag is too high, it will directly cause the polysilicon to be contaminated. Therefore, it is necessary to improve the production process and formula to obtain a polyethylene raw material with excellent puncture resistance and extremely low impurity content for preparing the polysilicon packaging film. Summary of the Invention

[0008] In order to solve the above problems existing in the prior art, the purpose of the present invention is to provide a linear low-density metallocene polyethylene resin, a linear low-density metallocene polyethylene packaging film suitable for polysilicon packaging bags, and its preparation method. By improving the cleanliness and mechanical properties of the linear low-density metallocene polyethylene as the raw material of the polysilicon packaging bag, the performance of the polysilicon packaging bag is improved.

[0009] To achieve the above purpose, the present invention adopts the following technical solutions.

[0010] In the first aspect, the present invention provides a linear low-density metallocene polyethylene resin. The melt flow rate (or melt index or melt flow index) of the linear low-density metallocene polyethylene resin is 0.7 g / 10 min to 1.3 g / 10 min (test conditions: 190 °C, 2.16 kg). The linear low-density metallocene polyethylene resin is obtained according to the following preparation method:

[0011] 1) In the gas-phase polymerization process, using a material including ethylene, hydrogen, comonomer, nitrogen, and a condensing agent as raw materials, adjusting the gas-phase components in the reactor, and completing the polymerization reaction with a metallocene catalyst to obtain a linear low-density metallocene polyethylene powder; wherein, the comonomer is a blend of hexene and octene, and the molar ratio of hexene to octene is 3:2 to 4:1;

[0012] 2) Mix the linear low density metallocene polyethylene powder, antioxidant and auxiliary antioxidant, and then carry out kneading and melting to obtain a linear low density metallocene polyethylene resin.

[0013] For the above linear low density metallocene polyethylene resin, in step 1), the molecular weight of the linear low density metallocene polyethylene powder obtained is 60,000 g / mol to 350,000 g / mol, and the molecular weight distribution index is 1 to 4; the density of the linear low density metallocene polyethylene powder is 0.910 g / cm 3 to 0.928 g / cm 3 .

[0014] For the above linear low density metallocene polyethylene resin, in step 1), the total molar concentration of hexene and octene accounts for 1.4% to 18% of the molar concentration of ethylene. That is, the total molar concentration of hexene and octene is 1.4% to 18% of the molar concentration of ethylene.

[0015] The present invention uses a blend of hexene and octene as a comonomer to control the molecular structure of the metallocene polyethylene resin (mPE) (specifically, the present invention controls the density of the linear low density metallocene polyethylene resin by controlling the ratio of the comonomer (hexene and octene) to ethylene), and obtains a linear low density metallocene polyethylene resin (mLLDPE) with a linear molecular structure, which is beneficial to improving the puncture resistance of mLLDPE.

[0016] For the above linear low density metallocene polyethylene resin, in step 1), the ethylene partial pressure in the gas phase component is 2500 KPa to 2700 KPa.

[0017] For the above linear low density metallocene polyethylene resin, in step 1), in the gas phase component, the molar ratio of hydrogen to ethylene is 0.0001 to 0.0003:1.

[0018] The present invention controls the melt flow ratio (MFR) of the product by the ratio of hydrogen to ethylene, thereby controlling the molecular weight distribution index of the linear low density metallocene polyethylene powder. In addition, the present invention adjusts the gas phase component in the reactor so that the ethylene partial pressure in the gas phase component is 2500 KPa to 2700 KPa, and the molar ratio of hydrogen to ethylene is 0.0001 to 0.0003:1, which can appropriately increase the reaction activity, and through the polymerization reaction, a puncture-resistant linear low density metallocene polyethylene powder is obtained.

[0019] For the above linear low density metallocene polyethylene resin, in step 2), the antioxidant includes 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid n-octadecyl ester (molecular formula C 35 H 62 O 3), and at least one of pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0020] For the above linear low density metallocene polyethylene resin, the auxiliary antioxidant includes at least one of tris(2,4-di-tert-butylphenyl) phosphite (molecular formula: C 42 H 63 O 3 P), tris(nonylphenyl) phosphite, and distearyl pentaerythritol diphosphite.

[0021] In the present invention, only common antioxidants and auxiliary antioxidants are used in the linear low density metallocene polyethylene powder, and processing aids such as zinc stearate or calcium stearate are not used, ensuring that the obtained linear low density metallocene polyethylene resin does not contain any metal element impurities and has a high purity. This high purity is beneficial for the linear low density metallocene polyethylene packaging film applicable to polysilicon packaging bags prepared later to have a very low static electricity content, so that the linear low density metallocene polyethylene packaging film applicable to polysilicon packaging bags does not affect the resistivity of the polysilicon stored therein.

[0022] The linear low density metallocene polyethylene resin (mLLDPE) prepared by the present invention has tensile resistance, puncture resistance, impact resistance, and tear resistance properties. In addition, it has the characteristic of high purity, so that the linear low density metallocene polyethylene packaging film applicable to polysilicon packaging bags produced using the mLLDPE of the present invention as a raw material has a low static electricity content, low surface impurity and bulk impurity content, high tensile properties, puncture strength, and heat sealing properties, and is more suitable as a packaging bag for polysilicon than conventional packaging films.

[0023] For the above linear low density metallocene polyethylene resin, in step 2), based on the mass of the linear low density metallocene polyethylene powder, the mass fraction of the antioxidant is 0.001% to 0.5%, and the mass fraction of the auxiliary antioxidant is 0.01% to 0.5%.

[0024] For the above linear low density metallocene polyethylene resin, in step 2), based on the mass of the linear low density metallocene polyethylene powder, the mass fraction of the antioxidant is 0.005% to 0.1%.

[0025] For the above linear low density metallocene polyethylene resin, in step 2), based on the mass of the linear low density metallocene polyethylene powder, the mass fraction of the auxiliary antioxidant is 0.05% to 0.3%.

[0026] For the above linear low density metallocene polyethylene resin, in step 2), based on the mass of the linear low density metallocene polyethylene powder, the mass fraction of the antioxidant is 0.01% to 0.05%, and the mass fraction of the auxiliary antioxidant is 0.1% to 0.2%.

[0027] For the above linear low density metallocene polyethylene resin, in step 2), the mixing and melting is carried out by a twin-screw extruder.

[0028] In the present invention, the melt flow rate of the linear low density metallocene polyethylene resin is tested according to the standard in GB / T 3682. At a temperature of 190 °C and a load of 2.16 kg, the melt flow rate is 0.7 g / 10 min to 1.3 g / 10 min.

[0029] The puncture strength of the above linear low density metallocene polyethylene resin at a film thickness of 0.3 mm is ≥5 N.

[0030] In the present invention, during the extrusion process of the twin-screw extruder, the linear low density metallocene polyethylene powder, the antioxidant and the auxiliary antioxidant are mixed and then added to the barrel of the extruder for mixing and melting in a certain proportion. By adjusting the contents of the antioxidant and the auxiliary antioxidant, a linear low density metallocene polyethylene resin (mLLDPE) with a melt flow rate of 0.7 g / 10 min to 1.3 g / 10 min (190 °C, 2.16 kg), a molecular weight distribution index of 2 to 4, and a puncture strength of ≥5 N (when the film thickness is 0.3 mm) and having high purity and puncture resistance is obtained.

[0031] The present invention produces a linear low density metallocene polyethylene powder with super strong puncture strength by adjusting the production process; by changing the reaction conditions and the additive formulation, the impurities in the linear low density metallocene polyethylene powder are reduced, and finally a linear low density metallocene polyethylene resin with high purity and puncture resistance is obtained. Using the linear low density metallocene polyethylene resin of the present invention as a raw material for the polysilicon packaging bag, the processed polysilicon packaging bag has excellent puncture resistance and extremely low surface impurity concentration.

[0032] In the second aspect, the present invention provides a preparation method of a linear low density metallocene polyethylene resin.

[0033] In the third aspect, the present invention provides a linear low density metallocene polyethylene packaging film suitable for polysilicon packaging bags. The linear low density metallocene polyethylene packaging film suitable for polysilicon packaging bags includes an inner layer, a middle layer and an outer layer, and the mass ratio of the inner layer, the middle layer and the outer layer is 1:(0.9 to 1.1):(0.9 to 1.1); wherein,

[0034] The inner layer comprises mLLDPE and a slip agent, and the mass ratio of the mLLDPE to the slip agent is 8:1.8 to 2.2;

[0035] The middle layer comprises mLLDPE and a slip agent, and the mass ratio of the mLLDPE to the slip agent is 8.9 to 9.1:1;

[0036] The outer layer comprises mLLDPE;

[0037] The mLLDPE is a linear low-density metallocene polyethylene resin, which is prepared by the preparation method of the above linear low-density metallocene polyethylene resin.

[0038] Since the mLLDPE is prepared by the preparation method of the above linear low-density metallocene polyethylene resin, the mLLDPE has the characteristics and properties of linear low-density metallocene polyethylene powder, especially the puncture resistance. In order to make the puncture resistance of the linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags more excellent, in the present invention, the dosage of the mLLDPE raw materials used in the inner layer, the middle layer to the outer layer film increases in turn.

[0039] For the above linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags, the slip agent comprises one of erucic acid amide and oleic acid amide.

[0040] For the above linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags, the thickness ratio of the inner layer, the middle layer and the outer layer is 1:2:1.

[0041] In the present invention, the middle layer of the linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags is designed to be thicker. It can be that more mLLDPE raw materials are added to the middle layer, which can reduce the cost while increasing the film thickness and the stiffness of the film. Then, combined with the inner layer and the outer layer with a slip agent added on the basis of the mLLDPE raw materials, the linear low-density metallocene polyethylene packaging film prepared has better mechanical properties and puncture resistance, and is more suitable for the storage of polysilicon.

[0042] For the above linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags, the total thickness of the inner layer, the middle layer and the outer layer is 180 μm to 300 μm.

[0043] For the above linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags, the properties of the linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags are: the film tensile strength (longitudinal / transverse) ≥ 46 MPa, the film yield stress (longitudinal / transverse) ≥ 12 MPa, the film right-angle tear strength (longitudinal / transverse) ≥ 110 kN / m, the film dart impact strength ≥ 1370 g, and the puncture strength ≥ 5 N.

[0044] In the present invention, the performance of the linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags is detected according to the national standard GB / T 1040. When measuring, the film thickness of the linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags is 0.3 mm.

[0045] Fourthly, the present invention provides a preparation method of a linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags, comprising the following steps:

[0046] (1) Obtaining linear low-density metallocene polyethylene powder;

[0047] (2) Obtaining linear low-density metallocene polyethylene resin (the linear low-density metallocene polyethylene resin is in pellet form);

[0048] (3) According to the above-mentioned linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags, a linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags is prepared by three-layer co-extrusion blown film.

[0049] In the above-mentioned preparation method of the linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags, in step (3), before three-layer co-extrusion blown film, the required amount of mLLDPE is blended with a slip agent.

[0050] In the above-mentioned preparation method of the linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags, the blown film is carried out by a three-layer co-extrusion blown film machine.

[0051] According to the technical solution of the present invention, first, in the gas-phase polymerization process, using a material including ethylene, hydrogen, comonomer, nitrogen and a condensing agent as raw materials, a polymerization reaction is completed by using a metallocene catalyst. By adjusting the type of comonomer (using a blend of hexene and octene as the comonomer) and the ratio, the molecular structure of the linear low-density metallocene polyethylene powder is controlled; based on the ethylene feed rate, the total molar ratio of hexene and octene is controlled to be 1.4% to 18%, and the molar ratio of hexene and octene added is 3:2 to 4:1 to obtain a puncture-resistant linear low-density metallocene polyethylene powder. Secondly, by adjusting the polymerization reaction parameters (ethylene partial pressure, hydrogen / ethylene molar ratio), the reaction activity is enhanced, and the metal residue amount of the linear low-density metallocene polyethylene powder is sufficiently reduced. Furthermore, by changing the additive components, the content of metals and impurities in the linear low-density metallocene polyethylene resin is reduced, and finally a high-purity linear low-density metallocene polyethylene resin is obtained. Finally, the above-mentioned linear low-density metallocene polyethylene resin is blended with a certain amount of slip agent, and a linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags is prepared by blowing film with a three-layer co-extrusion blown film machine.

[0052] In the present invention, without conflict, the above technical features can be freely combined to form new technical solutions.

[0053] The technical solution of the present invention has the following beneficial technical effects compared with the prior art:

[0054] (1) By changing the comonomers of the polymerization reaction, the molecular chain structure of the linear low-density metallocene polyethylene powder is changed, so that the puncture resistance of the linear low-density metallocene polyethylene powder is greatly improved;

[0055] (2) By optimizing the gas-phase components of the polymerization reaction, the reaction activity is improved, the residual amount of the catalyst in the resin is reduced, and thus the metal element content in the resin is greatly reduced; at the same time, by optimizing the additive components, the introduction of impurities is reduced, and thus the metal element content in the resin product is further reduced, and a high-purity puncture-resistant linear low-density metallocene polyethylene resin is obtained;

[0056] (3) By using the above high-purity puncture-resistant linear low-density metallocene polyethylene resin, a linear low-density metallocene polyethylene packaging film suitable for polysilicon packaging bags is prepared, with a surface impurity concentration ≤ 25 ppbw, a bulk impurity concentration ≤ 800, a puncture strength > 11 N, a heat-sealing strength ≥ 30 N, a breaking force ≥ 30 N / 15 mm, an elongation at break ≥ 900%, and an electrostatic content ≤ 0.05 kv. Specific Embodiments

[0057] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

[0058] Some embodiments of the present invention provide a method for preparing a linear low-density metallocene polyethylene resin, including the following steps:

[0059] S1: In the gas-phase polymerization process, using a material including ethylene, hydrogen, comonomers, nitrogen, and a condensing agent as raw materials, adjusting the gas-phase components in the reactor, and completing the polymerization reaction using a metallocene catalyst to obtain a linear low-density metallocene polyethylene powder; wherein, the comonomers are a blend of hexene and octene, and the molar ratio of hexene to octene is 3:2 to 4:1;

[0060] S2: Mix the linear low-density metallocene polyethylene powder prepared in step S1 with an antioxidant and a co-antioxidant, and then conduct kneading and melting to obtain a linear low-density metallocene polyethylene resin.

[0061] In some embodiments, in step S1, the total molar concentration of hexene and octene accounts for 1.4% to 18% of the molar concentration of ethylene. That is, the total molar concentration of hexene and octene is 1.4% to 18% of the molar concentration of ethylene (for example, 2%, 5%, 8%, 10%, 12%, 15% or 17%).

[0062] In some embodiments, in step S1, the partial pressure of ethylene in the gas phase component is 2500 KPa to 2700 KPa (for example, 2550 KPa, 2600 KPa, 2650 KPa or 2680 KPa).

[0063] In some embodiments, in step S1, in the gas phase component, the molar ratio of hydrogen to ethylene is 0.0001 to 0.0003:1 (for example, 0.0002:1).

[0064] In some embodiments, in step S1, the molecular weight of the linear low-density metallocene polyethylene powder is 60000 g / mol to 350000 g / mol (for example, 80000 g / mol, 100000 g / mol, 150000 g / mol, 200000 g / mol, 250000 g / mol, 300000 g / mol or 330000 g / mol), the molecular weight distribution index is 1 to 4 (for example, 2 or 3), and the density of the linear low-density metallocene polyethylene powder is 0.910 g / cm 3 to 0.928 g / cm 3 (for example, 0.920 g / cm 3 )

[0065] In some embodiments, in step S2, based on the mass of the linear low density metallocene polyethylene powder, the mass fraction of the antioxidant is 0.001% to 0.5% (for example, 0.005%, 0.01%, 0.05%, 0.1%, 0.2%, 0.3% or 0.4%), and the mass fraction of the auxiliary antioxidant is 0.01% to 0.5% (for example, 0.03%, 0.05%, 0.1%, 0.2%, 0.3% or 0.4%); preferably, the mass fraction of the antioxidant is 0.005% to 0.1% (for example, 0.006%, 0.008%, 0.01%, 0.03%, 0.05% or 0.08%), and the mass fraction of the auxiliary antioxidant is 0.05% to 0.3% (for example, 0.06%, 0.08%, 0.10%, 0.15%, 0.20%, 0.25% or 0.28%); more preferably, the mass fraction of the antioxidant is 0.01% to 0.05% (for example, 0.02%, 0.03% or 0.04%), and the mass fraction of the auxiliary antioxidant is 0.1% to 0.2% (for example, 0.12%, 0.14%, 0.15%, 0.17% or 0.19%).

[0066] In some embodiments, in step S2, the antioxidant includes at least one of n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (molecular formula: C 35 H 62 O 3 ), and pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate]; the auxiliary antioxidant includes at least one of tris(2,4-di-tert-butylphenyl) phosphite (molecular formula: C 42 H 63 O 3 P), tris(nonylphenyl) phosphite, and pentaerythritol diphosphite distearyl ester.

[0067] In some embodiments, in step S2, the mixing and melting is carried out using a twin-screw extruder.

[0068] Some embodiments of the present invention also provide a linear low density metallocene polyethylene resin, which is prepared by the above preparation method.

[0069] In some embodiments, the melt flow rate (or melt index or melt flow index) of the linear low density metallocene polyethylene resin is 0.7 g / 10 min to 1.3 g / 10 min (for example, 0.8 g / 10 min, 0.9 g / 10 min, 1.0 g / 10 min or 1.23 g / 10 min), and the puncture strength of the linear low density metallocene polyethylene resin at a film thickness of 0.3 mm is ≥5 N.

[0070] In the present invention, during the extrusion process of a twin-screw extruder, linear low-density metallocene polyethylene powder, an antioxidant, and a co-antioxidant are mixed and then added to the barrel of the extruder for kneading and melting in a certain proportion. By adjusting the contents of the antioxidant and the co-antioxidant, a linear low-density metallocene polyethylene resin with a melt flow rate of 0.7 g / 10 min to 1.3 g / 10 min (at 190 °C, 2.16 kg), a molecular weight distribution index of 2 to 4, and a puncture strength ≥ 5 N (when the film thickness is 0.3 mm) and having high purity and puncture resistance is obtained.

[0071] Some embodiments of the present invention also provide a linear low-density metallocene polyethylene packaging film suitable for polysilicon packaging bags. The linear low-density metallocene polyethylene packaging film suitable for polysilicon packaging bags includes an inner layer, a middle layer, and an outer layer. The mass ratio of the inner layer, the middle layer, and the outer layer is 1:0.9 to 1.1:0.9 to 1.1 (for example, 1:1:1); wherein,

[0072] The inner layer includes mLLDPE and a slip agent, and the mass ratio of the mLLDPE to the slip agent is 8:1.8 to 2.2 (for example, 8:2);

[0073] The middle layer includes mLLDPE and a slip agent, and the mass ratio of the mLLDPE to the slip agent is 8.9 to 9.1:1 (for example, 9:1);

[0074] The outer layer includes mLLDPE;

[0075] The mLLDPE is a linear low-density metallocene polyethylene resin prepared by using the preparation method of the above-mentioned linear low-density metallocene polyethylene resin.

[0076] In some embodiments, the slip agent includes at least one of erucamide and oleamide.

[0077] In some embodiments, the layer thickness ratio of the inner layer, the middle layer, and the outer layer is 1:2:1, and the total thickness of the inner layer, the middle layer, and the outer layer is 180 μm to 300 μm (for example, 200 μm, 220 μm, 250 μm, or 280 μm).

[0078] In some embodiments, the properties of the linear low-density metallocene polyethylene packaging film suitable for polysilicon packaging bags are as follows: the film tensile strength (longitudinal / transverse) ≥ 46 MPa, the film yield stress (longitudinal / transverse) ≥ 12 MPa, the film right-angle tear strength (longitudinal / transverse) ≥ 110 kN / m, the film dart impact strength ≥ 1370 g, and the puncture strength ≥ 5 N.

[0079] Unless otherwise specified, various raw materials, reagents, instruments, and equipment used in this application can be obtained through market purchases or prepared by existing methods. For the experimental methods without specific conditions noted in the following examples, they are usually determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer. For example, the melt flow rate of linear low-density metallocene polyethylene resin is tested according to the standard in GB / T 3682; the properties of the linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags are tested according to the standard of GB / T 1040 "Determination of Tensile Properties of Plastics".

[0080] Example 1

[0081] A preparation method of a linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags, comprising the following steps:

[0082] S1: In the gas-phase polymerization process, using ethylene, hydrogen, comonomer, nitrogen, condensate, etc. as raw materials, the polymerization reaction is completed with a metallocene catalyst. Specifically, during the polymerization reaction, the gas-phase components in the reactor are adjusted to appropriately increase the reaction activity. Among them, in the gas-phase components, the ethylene partial pressure is 2500 KPa, the molar ratio of hydrogen to ethylene is 0.00025:1, the reaction activity is 8200 kg / kg, the comonomer is a blend of hexene and octene, the total molar amount of the hexene and octene is 1.5% of the molar amount of ethylene used, and the molar ratio of hexene to octene added is 4:1; linear low-density metallocene polyethylene powder is obtained through the polymerization reaction;

[0083] S2: During the extrusion process of a twin-screw extruder, the linear low-density metallocene polyethylene powder is fully mixed with a compound antioxidant. Among them, the compound antioxidant includes an antioxidant (n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) and a co-antioxidant (tris[2,4-di-tert-butylphenyl]phosphite). The addition amounts of the antioxidant and the co-antioxidant are 0.03% and 0.15% of the mass of the linear low-density metallocene polyethylene powder respectively; after mixing, it is sent into the barrel of the extruder for mixing and melting to obtain a linear low-density metallocene polyethylene resin with a melt flow rate of 1.03 g / 10 min (190 °C, 2.16 kg), a density of 0.9190 g / cm 3 , a molecular weight distribution index of 2.3, and a puncture strength ≥ 5.7 N (when the film thickness is 0.3 mm).

[0084] S3: Using the linear low-density metallocene polyethylene resin obtained in step S2, it is blended with a certain amount of slip agent, single-layer and single-material, and a linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags is produced by blowing film with a three-layer co-extrusion blown film machine. Specifically,

[0085] The three layers of raw materials are prepared according to the following raw material ratios by weight:

[0086] Inner layer: 10 parts, among which, the mass ratio of mLLDPE to the slip agent is 8:2;

[0087] Middle layer: 10 parts, among which, the mass ratio of mLLDPE to the slip agent is 9:1;

[0088] Outer layer: 10 parts of mLLDPE;

[0089] The thickness ratio of the inner layer, middle layer and outer layer in the three layers is 1:2:1, and the total thickness is 200 μm.

[0090] Example 2

[0091] A preparation method of a linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags includes the following steps:

[0092] S1: In the gas-phase polymerization process, using ethylene, hydrogen, comonomer, nitrogen, condensate, etc. as raw materials, and using a metallocene catalyst to complete the polymerization reaction. Specifically, during the polymerization reaction, adjust the gas-phase components in the reactor to appropriately increase the reaction activity. Among them, in the gas-phase components, the ethylene partial pressure is 2600 KPa, the hydrogen / ethylene molar ratio is 0.0002:1, the reaction activity is 8300 kg / kg, the comonomer is a blend of hexene and octene, and the total molar amount of hexene and octene is 1.7% of the molar amount of ethylene used; the molar ratio of hexene to octene is 3:2; linear low-density metallocene polyethylene powder is obtained through the polymerization reaction;

[0093] S2: During the extrusion process of a twin-screw extruder, fully mix the linear low-density metallocene polyethylene powder with a composite antioxidant. Among them, the composite antioxidant includes an antioxidant (n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate) and a co-antioxidant (tris[2,4-di-tert-butylphenyl] phosphite). The addition amounts of the antioxidant and the co-antioxidant are 0.025% and 0.18% of the mass of the linear low-density metallocene polyethylene powder respectively. Then, send it into the barrel of the extruder for mixing and melting to obtain a linear low-density metallocene polyethylene resin with a melt flow rate of 1.01 g / 10 min (190 °C, 2.16 kg), a density of 0.9189 g / cm 3 , a molecular weight distribution index of 2.5, and a puncture strength ≥ 6.2 N (when the film thickness is 0.3 mm);

[0094] S3: Using the linear low-density metallocene polyethylene resin obtained in step S2, blend it with a certain amount of slip agent, single-layer single-material, and blow a film through a three-layer co-extrusion blown film machine to obtain a linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags. Specifically,

[0095] The three-layer raw materials are prepared according to the following raw material ratios by weight:

[0096] Inner layer: 10 parts, among which, the mass ratio of mLLDPE to the slip agent is 8:2;

[0097] Middle layer: 10 parts, among which, the mass ratio of mLLDPE to the slip agent is 9:1;

[0098] Outer layer: 10 parts of mLLDPE;

[0099] The thickness ratio of the inner layer, middle layer and outer layer in the three layers is: 1:2:1, and the total thickness is 200 μm.

[0100] Comparative Example 1

[0101] A preparation method of a polyethylene packaging film applicable to a polysilicon packaging bag, comprising the following steps:

[0102] Mix low-density polyethylene resins (LDPE-A, LDPE-B and LDPE-C) with melt indexes of 0.9 g / 10 min to 1 g / 10 min, 2.1 g / 10 min to 2.9 g / 10 min, and 0.2 g / 10 min to 0.5 g / 10 min evenly according to a mass ratio of 90:5:20, and prepare a single-layer polysilicon packaging film by the casting method of plastic film, with a film thickness of 250 μm; among them,

[0103] The density of LDPE-A is 0.910 g / cm 3 to 0.925 g / cm 3 , and the molecular weight distribution index is 4 to 15;

[0104] The density of LDPE-B is 0.910 g / cm 3 to 0.925 g / cm 3 , and the molecular weight distribution index is 4 to 15;

[0105] The density of LDPE-C is 0.910 g / cm 3 to 0.925 g / cm 3 , and the molecular weight distribution index is 4 to 15.

[0106] Comparative Example 2

[0107] A preparation method of a polyethylene packaging film applicable to a polysilicon packaging bag, comprising the following steps:

[0108] The inner layer is formulated with metallocene polyethylene resin having a melt index of 0.9 g / 10 min to 1 g / 10 min, LLDPE with a melt index of 2.1 g / 10 min to 2.9 g / 10 min, and LDPE with a melt index of 0.2 g / 10 min to 0.5 g / 10 min; wherein, the density of the metallocene polyethylene resin is 0.910 g / cm 3 to 0.925 g / cm 3 , and the molecular weight distribution index is 2 to 5; the density of the LLDPE is 0.910 g / cm 3 to 0.925 g / cm 3 , and the molecular weight distribution index is 2 to 5; the density of the LDPE is 0.910 g / cm 3 to 0.925 g / cm 3 , and the molecular weight distribution index is 4 to 15;

[0109] The middle layer is formulated with metallocene polyethylene resin having a melt index of 0.9 g / 10 min to 1 g / 10 min (using the same metallocene polyethylene resin as the inner layer) and LLDPE with a melt index of 2.1 g / 10 min to 2.9 g / 10 min (using the same LLDPE raw material as the inner layer) as the middle layer formulation, wherein the mass ratio of the metallocene polyethylene resin to the LLDPE is (60 to 70):(40 to 30);

[0110] The outer layer uses LDPE (using the same LDPE raw material as the inner layer) as the raw material, and three-layer co-extrusion is carried out, with a film thickness of 220 μm, and the thickness ratio of the inner layer, middle layer, and outer layer in the three layers is 1:2:1.

[0111] Comparative Example 3

[0112] A preparation method of a linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags, comprising the following steps:

[0113] S1: Prepare metallocene polyethylene base powder by a conventional method; in the gas-phase polymerization process, using ethylene, hydrogen, comonomer, nitrogen, condensing agent, etc. as raw materials, and complete the polymerization reaction with a metallocene catalyst. Specifically, during the polymerization reaction, among the gas-phase components, the ethylene partial pressure is 2200 KPa, the molar ratio of hydrogen to ethylene is 0.00024:1, the reaction activity is 6000 kg / kg to 7000 kg / kg, the comonomer is hexene, and the total molar amount of the hexene is 1.0% to 1.8% of the molar amount of ethylene used; obtain conventional metallocene polyethylene powder through the polymerization reaction;

[0114] S2: Prepare metallocene polyethylene resin:

[0115] During the extrusion process of a twin-screw extruder, metallocene polyethylene powder is fully mixed with a compound antioxidant. The compound antioxidant includes an antioxidant (n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), a co-antioxidant (tris(2,4-di-tert-butylphenyl) phosphite), and a processing aid (zinc stearate). The addition amounts of the antioxidant, co-antioxidant, and processing aid are 0.03%, 0.15%, and 0.04% of the mass of the metallocene polyethylene powder, respectively. After mixing, it is sent into the barrel of the extruder for kneading and melting to obtain a conventional metallocene polyethylene resin with a melt flow rate of 1.01 g / 10 min (test conditions: 190 °C, 2.16 kg), a density of 0.9200 g / cm 3 , a molecular weight distribution index of 2.5, and a puncture strength of 3 N (when the film thickness is 0.3 mm).

[0116] S3: Using the conventional metallocene polyethylene resin obtained in step S2, it is blended with a certain amount of slip agent, single-layer and single-material, and blown into a linear low-density metallocene polyethylene packaging film suitable for polysilicon packaging bags through a three-layer co-extrusion blown film machine. Specifically,

[0117] The three-layer raw materials are prepared according to the following raw material ratios by weight:

[0118] Inner layer: It includes metallocene polyethylene resin and a slip agent, with a total mass of 10 parts. Among them, the mass ratio of metallocene polyethylene resin to slip agent is 8:2;

[0119] Middle layer: It includes metallocene polyethylene resin and a slip agent, with a total mass of 10 parts. Among them, the mass ratio of metallocene polyethylene resin to slip agent is 9:1;

[0120] Outer layer: 10 parts of metallocene polyethylene resin;

[0121] The thickness ratio of the inner layer, middle layer, and outer layer in the three layers is 1:2:1, and the total thickness is 200 μm.

[0122] Comparative Example 4

[0123] A preparation method of a linear low-density metallocene polyethylene packaging film suitable for polysilicon packaging bags, including the following steps:

[0124] S1: Prepare metallocene polyethylene powder by conventional methods; in the gas-phase polymerization process, use ethylene, hydrogen, comonomer, nitrogen, condensing agent, etc. as raw materials, and complete the polymerization reaction with metallocene catalyst. Specifically, during the polymerization reaction, among the gas-phase components, the ethylene partial pressure is 2150 KPa, the molar ratio of hydrogen to ethylene is 0.00023:1, the reaction activity is 5800 kg / kg to 6500 kg / kg, the comonomer is hexene, and the total molar amount of the hexene is 1.0% to 1.8% of the molar amount of ethylene used; obtain conventional metallocene polyethylene powder through the polymerization reaction;

[0125] S2: Prepare metallocene polyethylene resin; specifically, during the extrusion process of the twin-screw extruder, fully mix the metallocene polyethylene powder with the compound antioxidant. Among them, the compound antioxidant includes antioxidant (n-octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate), auxiliary antioxidant (tris[2,4-di-tert-butylphenyl] phosphite), and processing aid. The addition amounts of the antioxidant, auxiliary antioxidant, and processing aid (zinc stearate) are 0.03%, 0.15%, and 0.04% of the mass of the metallocene polyethylene powder respectively; after mixing, send it into the barrel of the extruder for kneading and melting to obtain metallocene polyethylene resin mPE with a melt flow rate of 1.03 g / 10 min (test conditions: 190 °C, 2.16 kg), a density of 0.9198 g / cm 3 , a molecular weight distribution index of 2.4, and a puncture strength of 3.2 N (when the film thickness is 0.3 mm).

[0126] S3: Use the metallocene polyethylene resin mPE obtained in step S2, blend it with a certain amount of conventional LLDPE and slip agent, single-layer single-material, and blow film with a three-layer coextrusion blown film machine to obtain a metallocene polyethylene packaging film suitable for polysilicon packaging bags. Specifically,

[0127] The three-layer raw materials are prepared according to the following raw material ratios by weight:

[0128] Inner layer: LLDPE, mPE, and slip agent, with a total mass of 10 parts. Among them, the mass ratio of the total mass of LLDPE and mPE to the mass of the slip agent is 8:2; the mass ratio of LLDPE to mPE is 1:1;

[0129] Middle layer: LLDPE, mPE, and slip agent, with a total mass of 10 parts. Among them, the mass ratio of the total mass of LLDPE and mPE to the mass of the slip agent is 9:1; the mass ratio of LLDPE to mPE is 1:1;

[0130] Outer layer: LLDPE and mPE, with a total mass of 10 parts. Among them, the mass ratio of LLDPE to mPE is 1:1;

[0131] The thickness ratio of the inner, middle, and outer layers of the three layers is 1:2:1, and the total thickness is 200 μm.

[0132] Performance test:

[0133] According to the method in the standard of GB / T 1040 "Determination of Tensile Properties of Plastics", the performance of the polysilicon films prepared in the above-mentioned examples and comparative examples was tested. The results are shown in Table 1 below.

[0134] It can be seen from Table 1 that compared with the conventional metallocene polyethylene packaging films applicable to polysilicon packaging bags (Comparative Example 1 and Comparative Example 2), the linear low-density metallocene polyethylene packaging films applicable to polysilicon packaging bags prepared by using Examples 1 and 2 of the present invention have very excellent mechanical properties, and the contents of surface impurities, bulk impurities, and static electricity are all significantly reduced. The lower contents of surface impurities and bulk impurities indicate that the linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags has high purity; the lower static electricity content indicates that the linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags will not have an adverse effect on the resistivity of the polysilicon stored therein; the higher heat-sealing strength is beneficial to better storing the polysilicon stored in the packaging film. Otherwise, the low heat-sealing strength is likely to cause the seal of the packaging bag to be easily damaged, resulting in the exposure or leakage of polysilicon to the outside and being contaminated by external impurities.

[0135] In addition, the difference between Comparative Example 3 and Example 1 is that a metallocene polyethylene resin prepared by a conventional method (first preparing metallocene polyethylene powder by a conventional method, and then mixing the metallocene polyethylene powder with an antioxidant, a co-antioxidant, and a processing aid to obtain a resin) is used to prepare a metallocene polyethylene packaging film applicable to polysilicon packaging bags. The contents of surface impurities, bulk impurities, and static electricity of the obtained metallocene polyethylene packaging film applicable to polysilicon packaging bags are all higher than those of the packaging films of Examples 1 and 2, and the heat-sealing strength and puncture resistance are lower. In Comparative Example 4, a metallocene polyethylene resin prepared by a conventional method is combined with conventional LLDPE to prepare a metallocene polyethylene packaging film applicable to polysilicon packaging bags, and the performance of the obtained metallocene polyethylene packaging film applicable to polysilicon packaging bags is also not as excellent as that of the metallocene polyethylene packaging films obtained in Examples 1 and 2.

[0136] Therefore, the linear low-density metallocene polyethylene packaging film applicable to polysilicon packaging bags prepared by using the technical solution of the present invention has lower contents of surface impurities and bulk impurities, excellent performance, high heat-sealing strength and puncture resistance, and less static electricity content, and is more suitable for use as a polysilicon packaging bag.

[0137] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as the individual numbers within that range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0138] In the present application, unless otherwise stated, the orientation terms such as "upper" and "lower" specifically refer to directions. Additionally, in the description of the specification of the present application, the terms "comprising", "including", etc. mean "including but not limited to". In this text, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this text, "and / or" describes the association relationship of associated objects and indicates that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Wherein A and B can be singular or plural. In this text, "at least one" means one or more, and "a plurality" means two or more. "At least one kind", "at least one of the following (items)" or similar expressions refer to any combination of these items, including any combination of single item (s) or plural item (s).

[0139] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features claimed herein.

[0140] Table 1

[0141] 。

Claims

1. A linear low-density metallocene polyethylene resin, characterized in that The melt flow rate of the linear low-density metallocene polyethylene resin is 0.7 g / 10 min to 1.3 g / 10 min, and the linear low-density metallocene polyethylene resin is obtained according to the following preparation method: 1) In a gas phase polymerization process, using materials including ethylene, hydrogen, comonomer, nitrogen and condensing agent as raw materials, adjusting the gas phase components in the reactor, and using a metallocene catalyst to complete the polymerization reaction to obtain a linear low-density metallocene polyethylene powder; wherein the comonomer is a blend of hexene and octene, and the molar ratio of the hexene to the octene is 3:2 to 4:1; the total molar concentration of the hexene and octene is 1.4% to 18% of the molar concentration of ethylene; the ethylene partial pressure in the gas phase component is 2500 KPa to 2700 KPa; 2) mixing the linear low-density metallocene polyethylene powder, the antioxidant and the auxiliary antioxidant, and then kneading and melting to obtain a linear low-density metallocene polyethylene resin; wherein: The molecular weight of the linear low-density metallocene polyethylene powder obtained in step 1) is 60,000 g / mol to 350,000 g / mol, and the molecular weight distribution index is 1 to 4; the density of the linear low-density metallocene polyethylene powder is 0.910 g / cm 3 Up to 0.928 g / cm 3 ; In step 2), based on the mass of the linear low-density metallocene polyethylene powder, the mass fraction of the antioxidant is 0.001% to 0.5%, and the mass fraction of the auxiliary antioxidant is 0.01% to 0.5%.

2. The linear low density metallocene polyethylene resin according to claim 1, characterized in that In step 1), the molar ratio of hydrogen to ethylene in the gas phase component is 0.0001 to 0.0003:

1.

3. The linear low density metallocene polyethylene resin according to claim 2, characterized in that In step 2), the antioxidant includes at least one of 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate and pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate; The auxiliary antioxidant includes at least one of tris[2,4-di-tert-butylphenyl]phosphite, tris(nonylphenyl)phosphite and dioctadecyl pentaerythritol diphosphite.

4. The linear low density metallocene polyethylene resin according to claim 1, characterized in that In step 2), based on the mass of the linear low-density metallocene polyethylene powder, the mass fraction of the antioxidant is 0.005% to 0.1%; the mass fraction of the auxiliary antioxidant is 0.05% to 0.3%.

5. The linear low density metallocene polyethylene resin according to claim 1, 3 or 4, characterized in that: In step 2), the mixing and melting is carried out using a twin-screw extruder.

6. A linear low-density metallocene polyethylene packaging film suitable for polysilicon packaging bags, characterized in that: The linear low-density metallocene polyethylene packaging film suitable for polycrystalline silicon packaging bags comprises an inner layer, a middle layer and an outer layer, wherein the mass ratio of the inner layer, the middle layer and the outer layer is 1:0.9 to 1.1:0.9 to 1.1; wherein, The inner layer comprises mLLDPE and a lubricant, and the mass ratio of the mLLDPE to the lubricant is 8:1.8 to 2.2; The middle layer includes mLLDPE and a lubricant, and the mass ratio of the mLLDPE to the lubricant is 8.9 to 9.1:1; The outer layer comprises mLLDPE; The mLLDPE is the linear low-density metallocene polyethylene resin, which is the linear low-density metallocene polyethylene resin as described in any one of claims 1 to 4.

7. The linear low-density metallocene polyethylene packaging film suitable for polycrystalline silicon packaging bags according to claim 6, characterized in that: The lubricant includes at least one of erucamide and oleamide.

8. The linear low-density metallocene polyethylene packaging film suitable for polycrystalline silicon packaging bags according to claim 7, characterized in that: The thickness ratio of the inner layer, the middle layer and the outer layer is 1:2:

1.

9. The linear low-density metallocene polyethylene packaging film suitable for polycrystalline silicon packaging bags according to any one of claims 6 to 8, characterized in that: The total thickness of the inner layer, the middle layer and the outer layer is 180 μm to 300 μm.

10. A method for preparing a linear low-density metallocene polyethylene packaging film suitable for polycrystalline silicon packaging bags as claimed in claim 9, characterized in that: The method for preparing the linear low-density metallocene polyethylene packaging film suitable for polycrystalline silicon packaging bags comprises the following steps: (1) Obtaining linear low-density metallocene polyethylene powder; (2) obtaining a linear low-density metallocene polyethylene resin; (3) A linear low-density metallocene polyethylene packaging film suitable for polycrystalline silicon packaging bags according to any one of claims 6 to 9 is produced by three-layer co-extrusion blown film.

11. The method for preparing a linear low-density metallocene polyethylene packaging film suitable for polycrystalline silicon packaging bags according to claim 10, characterized in that: In the step (3), before the three-layer co-extrusion blown film is carried out, the required amount of mLLDPE and the lubricant are mixed.